There have been semiconductor chip modules called multichip modules (MCM) in which a plurality of silicon chips produced in different processes are mounted on a substrate. In such multichip modules, bare chips mounted in a bare state are used as silicon chips and the bare chips are connected to each other using a wire line formed on a ceramic or build-up substrate (Japanese Laid-open Patent Publication No. 06-283661).
In such multichip modules, a large amount of heat is generated during the operation of chips. Therefore, a build-up substrate is thinned by polishing or grinding in advance to increase the heat dissipation effect (Japanese Laid-open Patent Publication No. 07-37840).
However, all of the heat generated during the operation of chips may not be removed from the multichip module even if the method disclosed in Japanese Laid-open Patent Publication No. 07-37840 is employed. Thus, chips, a substrate, and other components disposed on the substrate may be subjected to thermal expansion and deformed owing to the heat. The deformation due to the thermal expansion causes fatigue failure of each component, which may shorten the life of multichip modules.